Thruster for Mars mission breaks records

Thruster for Mars mission breaks records
Scott Hall makes some final adjustments on the thruster before the test begins. Credit: NASA

An advanced space engine in the running to propel humans to Mars has broken the records for operating current, power and thrust for a device of its kind, known as a Hall thruster.

The development of the was led by Alec Gallimore, University of Michigan professor of and the Robert J. Vlasic Dean of Engineering.

Hall thrusters offer exceptionally efficient plasma-based spacecraft propulsion by accelerating small amounts of propellant very quickly using electric and magnetic fields. They can achieve top speeds with a tiny fraction of the fuel required in a chemical rocket.

"Mars missions are just on the horizon, and we already know that Hall thrusters work well in space," Gallimore said. "They can be optimized either for carrying equipment with minimal energy and propellant over the course of a year or so, or for speed—carrying the crew to Mars much more quickly."

The challenge is to make them larger and more powerful. The X3, a Hall thruster designed by researchers at U-M, NASA and the U.S. Air Force, shattered the previous thrust record set by a Hall thruster, coming in at 5.4 newtons of force compared with 3.3 newtons. The improvement in thrust is especially important for crewed mission—it means faster acceleration and shorter travel times. The X3 also more than doubled the operating current record (250 amperes vs. 112 amperes) and ran at a slightly higher power (102 kilowatts vs. 98 kilowatts).

The X3 is one of three prototype "Mars engines" to be turned into a full propulsion system with funding from NASA. Scott Hall, a doctoral student in aerospace engineering at U-M, carried out the tests at the NASA Glenn Research Center in Cleveland, along with Hani Kamhawi, a NASA Glenn research scientist who has been heavily involved in the development of the X3. The experiments were the culmination of more than five years of building, testing and improving the thruster.

Thruster for Mars mission breaks records
A side shot of the X3 firing at 50 kilowatts. Credit: NASA

NASA Glenn, which specializes in solar electric propulsion, is currently home to the only vacuum chamber in the U.S. that can handle the X3 thruster. The thruster produces so much exhaust that vacuum pumps at other chambers can't keep up. Then, xenon that has been shot out the back of the engine can drift back into the plasma plume, muddying the results. But as of January 2018, an upgrade of the vacuum chamber in Gallimore's lab will enable X3 testing right at U-M.

For now, the X3 team snagged a test window from late July through August this year, starting with four weeks to set up the thrust stand, mount the thruster and connect the thruster with xenon and electrical power supplies. Hall had built a custom thrust stand to bear the X3's 500-pound weight and withstand its force, as existing stands would collapse under it. Throughout the process, Hall and Kamhawi were supported by NASA researchers, engineers and technicians.

"The big moment is when you close the door and pump down the chamber," Hall said.

After the 20 hours of pumping to achieve a space-like vacuum, Hall and Kamhawi spent 12-hour days testing the X3.

Even small breakages feel like big problems when it takes days to gradually bring air back into the chamber, get in to make the repair and pump the air back out again. But in spite of the challenges, Hall and Kamhawi brought the X3 up to its record-breaking power, current and thrust over the 25 days of testing.

Looking ahead, the X3 will at last be integrated with the power supplies under development by Aerojet Rocketdyne, a rocket and missile propulsion manufacturer and lead on the propulsion system grant from NASA. In spring 2018, Hall expects to be back at NASA Glenn running a 100-hour test of the X3 with Aerojet Rocketdyne's power processing system.


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Hall thruster a serious contender to get humans to Mars

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Oct 24, 2017
200kg of engine to create 5N of force? (Without power supply mass nor payload)
It can only accelerate itself at 1/400g.
1g would be rather useful and comfortable for the journey but I guess that is some years away.

Keep up the good work; and when you've cracked confining the exhaust add the linear accelerator stage.

RNP
Oct 25, 2017
@EyeNStein
A rough estimate assuming an acceleration of g/400 - The engine could get itself to Mars orbit in about 36 days at Mars closest approach, (I assume acceleration for half the distance and decelerating the other half). Now, clearly the system must carry many times more mass than that of the engine alone, but I would say these numbers suggest that the technology shows great promise.

Oct 25, 2017
200kg of engine to create 5N of force? (Without power supply mass nor payload)
It can only accelerate itself at 1/400g.

Add the mass of the spacecraft and the acceleration will be somewhat lower (mitigated if they use several thrusters but not below the value for one thruster accelerating itself)
However the key issue is that you can continually thrust over days/weeks/months. It adds up.
Humans can do OK in zero g over some time. And on Mars they'll be under 1/3 g, anyhow, so now point in trying to get a 1g burn to conserve bone/muscle mass.

Use proton atpase ion confinement for your "linear accelerator stage". That way you'd have a dog's chance of getting coherence.

You're just stringing together random words from a science dictionary, aren't you?

Oct 25, 2017
Wonder what happened to VASIMR? Let's find out...

"The 200 kW VX-200 had executed more than 10,000 engine firings by 2013, while demonstrating greater than 70% thruster efficiency—relative to RF power input—with argon propellant at full power.

"In August 2017, Ad Astra reported completing its Year 2 milestones for the VASIMR electric plasma rocket engine. NASA gave approval for Ad Astra to proceed with Year 3 after reviewing completion of a 10-hour cumulative test of the 200SS™ rocket at 100kW

"In order to conduct a manned trip to "Mars in just 39 days",[38][39][40] the VASIMR would require an electrical power level delivered only by nuclear propulsion (specifically the nuclear electric type) by way of nuclear power in space."

Oct 25, 2017
I dunno about the VASIMR comparison, seems a bit like an apples-pears comparison. They're certainly related technologies, but they seem, to my non-expert opinion, to be rather different implementations of ion thrusting. VASIMR seems to be a higher thrust, but as such, has a considerably higher power consumption requirement.

Which seems to be why Hall effect is being pursued. If you look at the principle argument you present, that the power conusmption is so high as to require a (heavy) nuclear power generator, maybe taking the hit to the thrust in exchange for a better power efficiency is justified.

Oct 25, 2017
VASIMR seems to be a higher thrust, but as such, has a considerably higher power consumption requirement.

Which seems to be why Hall effect is being pursued. If you look at the principle argument you present, that the power conusmption is so high as to require a (heavy) nuclear power generator, maybe taking the hit to the thrust in exchange for a better power efficiency is justified.
VASIMR was big news a few years ago and a popular/unpopular topic here at physorg. Both are related and NASA-funded. VASIMR test array was supposed to be installed on the ISS.
http://www.americ...simr.jpg

"The lack of electrodes results in greater reliability, longer life, and enables a much higher power density than competing ion and Hall thruster."

RNP posted a mars transit of 30-40 days on 102 kilowatts which doesnt seem right in comparison to VASIMR.

Oct 26, 2017
Give me 1/3g and a craft that doesn't shape like a truncated ice cream cone and I'd take it for a spin. Mars in 7 days would be tolerable without taking a whole ISS worth of experiments to pass the time productively.

The WC would also work and my laptop wouldn't float away. Houston my YouTube has a problem..

Oct 26, 2017
Not to mention with a short transit time less food, air, and water mass to boost. Interesting little math problem there somewhere I think. There should be an optimal balance.

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